Many new wireless communication devices and systems include multiple antennas for use in communicating with other wireless devices. In a common implementation, one of these multiple-antenna wireless devices may be called upon to communicate with another wireless device using a communication technique known as multiple input/multiple output (MIMO). In a MIMO communication channel, both a transmitting device at one end of the channel and a receiving device at the other end of the channel utilize multiple antennas. In this manner, multiple separate “spatial channels” may be formed to allow communication via multiple “spatial streams.” It is often desirable, however, that these multiple-antenna devices also be compatible with older, single-antenna “legacy” devices that can only support communication using a single spatial stream.
To communicate with a single-antenna device using a single spatial stream, a multiple-antenna device can simply limit its operation to one of its available antennas. This technique, however, limits the transmit power of the multiple-antenna device to the output power capability of the power amplifier associated with the selected antenna. To reduce product size and cost, the current trend in wireless devices is to use highly integrated electronics. This strategy will often include integration of the power amplifiers of the wireless device within an integrated circuit (e.g., a radio frequency integrated circuit (RFIC), a system on a chip (SoC), etc.). The use of integrated circuit technology to implement the transmit power amplifiers will further limit the amount of transmit power that is available from a single antenna for supporting single spatial stream operation. To overcome this deficiency, techniques may be developed for utilizing multiple transmit antennas to support single stream transmission in a multiple-antenna device. When using multiple transmit antennas, the overall transmission power of a device is the combination of the transmit powers of the individual antennas (and their associated power amplifiers). Thus, a higher level of overall transmit power can be obtained. There is a need for techniques for implementing multiple-antenna, single stream wireless communication in an efficient manner.